From 042dc8706f8005c5ebb3f0d0eaee99fb722fb9c3 Mon Sep 17 00:00:00 2001 From: Russell King Date: Mon, 9 Jul 2018 10:28:12 +0100 Subject: [PATCH] UPSTREAM: ARM: spectre-v1: use get_user() for __get_user() Fixing __get_user() for spectre variant 1 is not sane: we would have to add address space bounds checking in order to validate that the location should be accessed, and then zero the address if found to be invalid. Since __get_user() is supposed to avoid the bounds check, and this is exactly what get_user() does, there's no point having two different implementations that are doing the same thing. So, when the Spectre workarounds are required, make __get_user() an alias of get_user(). Change-Id: I32e38a7635961822ffadaad256caf9a34268bd2a Acked-by: Mark Rutland Signed-off-by: Russell King Signed-off-by: Tao Huang (cherry picked from commit b1cd0a14806321721aae45f5446ed83a3647c914) --- arch/arm/include/asm/uaccess.h | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h index 1798521a96b9..7c9e682b4060 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -314,6 +314,16 @@ static inline void set_fs(mm_segment_t fs) #define user_addr_max() \ (segment_eq(get_fs(), KERNEL_DS) ? ~0UL : get_fs()) +#ifdef CONFIG_CPU_SPECTRE +/* + * When mitigating Spectre variant 1, it is not worth fixing the non- + * verifying accessors, because we need to add verification of the + * address space there. Force these to use the standard get_user() + * version instead. + */ +#define __get_user(x, ptr) get_user(x, ptr) +#else + /* * The "__xxx" versions of the user access functions do not verify the * address space - it must have been done previously with a separate @@ -330,12 +340,6 @@ static inline void set_fs(mm_segment_t fs) __gu_err; \ }) -#define __get_user_error(x, ptr, err) \ -({ \ - __get_user_err((x), (ptr), err); \ - (void) 0; \ -}) - #define __get_user_err(x, ptr, err) \ do { \ unsigned long __gu_addr = (unsigned long)(ptr); \ @@ -395,6 +399,7 @@ do { \ #define __get_user_asm_word(x, addr, err) \ __get_user_asm(x, addr, err, ldr) +#endif #define __put_user(x, ptr) \ ({ \